1. Field of the Invention
The present invention relates to a cooling device having a micro cooling fin, and more particularly, to a cooling device having a micro cooling fin employing a Micro ElectroMechanical System (MEMS).
2. Description of the Related Art
In conventional cooling devices for electronic equipment and parts, a plurality of cooling fins are installed in a single base, and a blast fan for forcibly inducing the flow of the air when necessary is integrated into a cooling device. For example, a heat releasing device for cooling the CPU of a computer includes a plurality of cooling fins 2 on a single base 1 and a cooling fan 3 for generating an air flow with respect to the cooling fins 2, as shown in FIG. 1. Such a cooling device employing a forced air flow method forcibly makes the air surrounding fins flow to release heat from the cooling fins, as shown in FIG. 2.
However, in such a conventional cooling device, cooling fins are fixed, and their surfaces are smooth, so a significantly thick heat boundary layer 4 is spontaneously formed on a cooling fin when the air flows along the smooth surface of the cooling fin, as shown in FIG. 3. As a result, heat cannot be effectively released from the cooling fin 2. This is because an air space 5 accumulated in a heat boundary layer serves to resist heat transfer so as to inhibit heat from being released from the surface of the cooling fin 2. Thermal resistance within the accumulated air space 5 increases as distance from the surface of the cooling fin 2 decreases. The air space 5 is motionless on the surface of the cooling fin 2, so only heat transfer due to diffusion effects occurs, and there is not convection. As shown in FIG. 3, the air is forcibly made to flow toward the cooling fin 2 by the blast fan 3 at a speed of V0. In a portion distance from the accumulated heat boundary layer 4 on the cooling fin 2, the air flows at a speed of about V0, but the air flows at a speed of about V1 which is less than V0 when it passes through the heat boundary layer 4. The air flows at a speed of V2 which is less than V1 in the underlying accumulated air space 5. The flow of the air actually halts on the surface of the cooling fin 2. The halt of the air flow is due to friction and viscous force working between the air and the cooling fin 2, in view of aerodynamics. Accordingly, a large cooling fin is required to release a large amount of heat. However, as the size of a cooling fin increases, the surface area of the cooling fin and thermal resistance increase. So, the size of a cooling device is larger, and a heat transfer rate per unit volume decreases. This goes against the trend of miniaturizing parts, for example, the parts of a computer.
To solve the above problems, it is a first object of the present invention to provide a cooling device with a micro cooling fin having an efficient heat releasing structure.
It is a second object of the present invention to provide a cooling device with its a micro cooling fin, which has a high efficiency of heat release and a small size.
Accordingly, to achieve the above objects of the invention, in one embodiment, there is provided a cooling device with a micro cooling fin. The cooling device includes a substrate, and a plurality of vibrating type cooling fins extending from the substrate.
In another embodiment, there is provided a cooling device with a micro cooling fin, including a substrate, a plurality of vibrating type cooling fins extending from the substrate, and a blast fan for ventilating the substrate to cool the substrate and the vibrating type cooling fins and for causing the vibrating type cooling fins to vibrate.
In a cooling device according to the present invention, the substrate is preferably a semiconductor substrate. It is preferable that each of the vibrating type cooling fins extends in parallel to the surface of the substrate, and a hollow portion is provided below each vibrating type cooling fin.
Meanwhile, it is preferable to install the blast fan such that the air can be sent to the substrate at a predetermined angle with respect to the level of the substrate.
It is preferable to allow each of the vibrating type cooling fins to have a resonance frequency corresponding to a flow rate given by the blast fan so that the vibrating type cooling fins resonate in response to the flowing air generated by the blast fan.
It is preferable to form a coating layer for giving stress to the surface of each of the vibrating type cooling fins on the surface of the vibrating type cooling fins.